In the manufacture of various types of tissue products such as facial tissue, bath tissue, paper towels and the like, the dried tissue web or tissue sheet coming off of the tissue machine is -initially wound into a parent roll by a reel and temporarily stored for further processing. Sometime thereafter, the parent roll is unwound and the tissue web is converted into a final product form.
In winding the tissue web into a large parent roll, it is important that the roll be wound in a manner which prevents major defects in the roll and which permits efficient conversion of the roll into the final product, whether it be boxes of facial tissue sheets, rolls of bath tissue, rolls of embossed paper towels, and the like. Ideally, the parent roll has an essentially cylindrical form, with a smooth cylindrical major surface and two smooth, flat, and parallel end surfaces. The cylindrical major surface and the end surfaces should be free of ripples, bumps, waviness, eccentricity, and wrinkles, i.e. the roll should be substantially uniform. Likewise, the parent roll must be stable, so that it does not depart from its cylindrical shape during storage or routine handling, i.e. the roll should be dimensionally stable. Defects can force entire parent rolls to be scrapped if they are rendered unsuitable for high speed conversion.
Large diameter tissue rolls, having a diameter between about 70 inches to 150 inches, are especially difficult to wind since the tissue sheet is relatively weak, highly compressible, and has a relatively high sheet-to-sheet coefficient of friction. These factors can make it difficult to wind a tight roll with a high wound-in-tension due to nip mechanics. During winding, the layers of a roll will often readjust from the action of the roll moving through the nip to progressively tighten the roll or increase the wound-in-tension. Because the tissue sheet is highly compressible and has a high sheet-to-sheet friction, using a large nip load often deforms the winding parent roll without generating much additional wound-in-tension because the tissue layers do not easily move relative to one another. The large nip load often leads to horse collaring where an outer ring of the roll becomes loose and eventually tears and rips apart. Also, since the tissue is weak, the incoming sheet tension must be kept at a relatively low level, which results in a more loosely wound parent roll having a low wound-in-tension. It is especially important to wind the initial portion of a large diameter roll tightly such that as the diameter and weight of the parent roll increases, the core shaft remains centered within the parent roll and the initial portion is able to support the heavier outer portion of the parent roll without excessive deformation during winding, unwinding, storage, or handling.
New tissue reels having an endless flexible belt, disclosed in U.S. Pat. No. 5,901,918 entitled Apparatus and Method for Winding Paper that issued May 11, 1999 to Klerelid et al., are effective in the winding of tissue and paper webs. Such reels and winding methods can be used to produce substantially uniform and dimensionally stable parent rolls of soft tissue webs having diameters on the order of 70 to 150 inches. Such parent rolls are disclosed in U.S. Pat. No. 5,944,273 entitled Parent Roll for Tissue Paper that issued Aug. 31, 1999 to Lin et al.
However, such reels require a center wind for properly winding the roll. As an example, the pressure in the nip as a result of the increasing roll diameter can vary between approximately 4 psi at the start and reduce to about 0.5 psi with a constant belt tension of approximately 40 lb/in. Since the nip pressure can vary greatly, a center wind is used to better structure the winding roll throughout the entire winding cycle. Furthermore, it can be difficult to obtain a tightly wound roll at the start, since a hard nip between the winding roll and an incompressible drum is not present. Because the existing reel must be replaced rather than retro-fitted, the high capital cost often does not result in a favorable net present value or pay back period to justify the replacement expense.
Conventional pope reels or drum reels are known such as the reel disclosed in U.S. Pat. No 3,743,199 entitled Method and Apparatus for Reeling Web Material that issued Jul. 3, 1973 to Karr et al. These reels have an incompressible drum against which the parent roll is pressed to wind the roll. While winding a large diameter parent roll, often it is not possible to load the roll against the drum with a sufficient force, without damaging the roll, in order to drive the large parent roll without slippage. Too high of a nip load can deform and damage the parent roll and actually results in more force to drive the roll since the roll is highly compressible and readily deformed by the nip load. A possible solution is to use a center wind, but this is an expensive option. Furthermore, existing reels without a center wind may not be convertible to a center wind due to space constraints or the existing design of the current reel.
U.S. Pat. No. 4,143,828 entitled Winder For Papermaking Machine that issued Mar. 13, 1979 to Braun et al. discloses a winder, similar to a pope reel, having an endless band that is used to drive the parent roll. However, the '828 patent fails to teach how to operate the winder to wind a large diameter parent roll. In particular, the patent teaches that the winding roll should preferably not be loaded against the incompressible drum, but rather a gap should be present to allow air to escape through the porous band. It further teaches to change the band tension to change the density of the wound roll. Discussion on the preferred nip load against the reel drum to wind large diameter rolls is not present. A mode of operation using only the belt tension makes it difficult to wind a large diameter parent roll, since the action of the band alone without the use of a center wind can make it difficult to wind a sufficiently tight roll at the start to support the final weight of the large roll.
Another problem with winding tissue is transporting the tissue from the drying cylinder to the reel. U.S. Pat. No. 6,797,115 entitled Method and Apparatus for Making a Creped Tissue With Improved Tactile Qualities While Improving Handling of the Web that issued Sep. 28, 2004 to Klerelid et al. discloses several possible machine configurations using a carrying fabric or belt to transport the tissue to the reel-up. The patent discusses carrying the creped web through a compression nip that compresses the tissue to reduce its thickness and increase its tactile qualities. The patent discusses that as a consequence of the thickness reduction, a lengthening of the web occurs in the machine direction that produces slack in the tissue web on the belt downstream of the compression. The patent further discusses that to avoid winding difficulties in the reel-up, the peripheral speed of the paper roll should exceed that of the belt in order to remove the slack before the tissue web is wound into a roll. The only way that the peripheral speed of the roll can exceed that of the belt is to use a center wind.
Therefore, there is still a need for an apparatus and method of winding paper webs, especially bulky tissue webs, with the ability to wind uniform large diameter parent rolls. There is also need for an apparatus and method of winding paper webs, especially bulky tissue webs, with the ability to wind uniform large diameter rolls using a reel without a center wind assist. There is also a need for an apparatus to transport the paper webs, especially bulky tissue webs, to the reel without excessive compression in order to wind large diameter rolls without a center wind assist.